Cellulosic fibers find wide usage in products which require absorbency. Ground wood pulp fibers, for example, are used extensively in the absorbent cores of disposable diapers, sanitary napkins, incontinent devices and the like. Cellulose material obtains its absorbent property from the existence of polar hydroxy groups on the cellulose molecule. However, the hydrophilicity of cellulosic fibers is not 100%. This is partially due to the lack of complete accessibility of the hydroxy groups on the fiber surfaces and partially due to the existence on the surface of at least some cellulosic fibers of hydrophobic materials, such as fatty acids.
The absorbent core of many dressings, sanitary protection pads etc. comprise ground wood pulp cellulosic fibers. When the fluid to be absorbed is blood or menstrual fluid, the viscosity of the fluid is higher, and hence the transport of fluids within the absorbent core is slower than with a fluid of lesser viscosity. In the present invention, the salt present at the edge of the advancing fluid will increase the ionic strength of the fluid and thus decrease the viscosity of the fluid. This viscosity reduction will enhance the wicking rate or fluid travel in the absorbent product.
In those products in which a superabsorbent polymer is admixed with cellulosic fiber to form an absorbent core, there is competition for any applied liquid between the superabsorbent and the capillary network of the cellulosic fiber. The capillary force provided by the cellulosic fiber tries to move the liquid away from the impact zone of, for instance, a disposable diaper, while the superabsorbent tries to immobilize the fluid. If the superabsorbent swelling is dominant too early, most of the fluid will be immobilized at or near the impact zone while the rest of the absorbent material remains unused or dry. In the worse case, the impact zone can be so swollen so as to prevent capillary transport of the liquid away from the impact zone. The presence of an ionic salt causes the superabsorbent to take up fluid and thus swell and gel at a much slower rate which allows time for the capillary structure of the cellulosic fibers to move the liquid away from the impact zone into other areas of an absorbent core. Hence, the efficacy of the absorbent cores is increased.
It is therefore an objective of the present invention to provide a more wettable cellulosic fiber.
It is a further objective to provide a cellulosic fiber which has the propensity to reduce the viscosity of blood and menstrual fluid and hence provide an improved absorbent media for use in bandages, dressings and sanitary protection devices.
It is yet another objective of this invention to provide a cellulosic fiber which when used in an absorbent media in combination with a superabsorbent polymer causes the superabsorbent polymer to absorb liquid more slowly and allows for greater fluid spread within the absorptive media, hence increasing the efficacy of the absorbent media.